The use of alternating current transformers as a pickup or sensing means to sense a current flow in a conductor has been recognized for many years. Typically, these devices utilize a magnetic circuit that can be opened and then closed around a conductor in order to link the magnetic field generated by the current flowing in a conductor. This linkage is then used to couple to a coil to generate a voltage that is representative of the amount of current being drawn through the conductor under investigation.
The prior art devices generally use a magnetic circuit that can be separated into two segments to encircle the conductor, and further have been used as a means of testing for current without continuously sensing its presence. When current transformers are designed to be used as a continuous sensing device they typically are manufactured to encircle a specific size of wire. That wire normally is embedded in the device, and the section of wire that is embedded in the device is normally then connected into the circuit to be monitored. These devices typically utilize a conventional magnetic circuit with the conductor segment that is built into the device being used as the transformer primary. These constructions are very expensive and inconvenient to use as current pickup devices.